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and the page p
0
that contains the key x
0
next to x, and releasing the short-duration
Xlockonx
0
:
insert-into-page
.T;p;x;y;
v
/
unlatch-and-unfix
.p; p
0
/
unlock
.T; x
0
; X; short-duration/
insert-index-record
.T;y;x;p/
Here the call
insert-index-record
.T;y;x;p/ inserts the index record .y;x;p/ into
the secondary index and logs the insertion with a redo-undo log record in the
name of transaction T . The logic of the call is similar to that of the plain call
insert
.T;x;y;
v
/ without the secondary-index update; it includes a traversal of the
secondary index for locating the index page that will hold the index record .y;x;p/,
with any structure modifications needed to accommodate the insertion, and, with
key-specific locking, the acquisition of the secondary-key-specific commit-duration
Xlockon.r;Y;y/and the short-duration X lock (or IX lock) on .r;Y;y
0
/,wherey
0
is the key next to y in secondary-key order.
Observe that because the latch on the data page p is released before the index
record is inserted, it may happen that the tuple .x; y;
v
/ no longer resides in page
p when the index record carrying that page-id arrives at the secondary index. We
have no other option than releasing the latch on p, because, if key-specific locking is
used, the insertion of the index record involves acquiring the secondary-key-specific
locks, which may cause lock waits, which are only allowed if no latches are held.
Inserting a tuple .x; y;
v
/ by transaction T generates the pair of redo-undo log
records:
n
1
:
h
T; I; p; x; y;
v
;n
0
i
n
2
:
h
T;
ix-I
;q;y;x;p;n
1
i
where p is the page-id of the data page that received the tuple .x; y;
v
/,andq is
the page-id of the leaf page of the secondary index that received the index record
.y;x;p/. The action name
ix-I
denotes the action of inserting an index record into
the secondary index. If the transaction rolls back, the following pair of redo-only
log records is written:
n
3
:
h
T;
ix-I
1
;q
0
;y;x;n
1
i
n
4
:
h
T; I
1
;p
0
;x;n
0
i
Here q
0
is the page-id of the leaf page that holds the index record .y;x;p/ and p
0
the page-id of the data page that holds the tuple .x; y;
v
/, at the time the undo actions
are performed.
11.3
Index Construction Without Quiescing Updates
We now tackle the problem of constructing a secondary index for a relation
r.X;Y;V/ during normal transaction processing when transactions are allowed
concurrent access to the relation. First we note that a trivial solution is obtained
